Hydrogenated block copolymer and composition comprising same

ABSTRACT

Provided are a block copolymer and a thermoplastic elastomer composition each of which is excellent in both tensile strength and elastic recovery, and has good abrasion resistance. Specifically, provided are a hydrogenated block copolymer, which is obtained by hydrogenating a block copolymer having two or more polymer blocks (a) each containing a structural unit derived from an aromatic vinyl compound and one or more polymer blocks (b) each containing structural units derived from isoprene and 1,3-butadiene, in which the hydrogenated block copolymer has a crystallization peak temperature (Tc) defined as described below of −3 to 15° C., and a thermoplastic elastomer composition containing the hydrogenated block copolymer: (crystallization peak temperature (Tc)) a peak top temperature of an exothermic peak observed when the temperature of a sample is increased from 30° C. to 150° C. at a rate of temperature increase of 10° C./min and then the sample is cooled to −100° C. at a rate of temperature decrease of 10° C./min, the peak top temperature being measured with differential scanning calorimeter (DSC), is defined as the crystallization peak temperature (Tc).

TECHNICAL FIELD

The present invention relates to a hydrogenated block copolymerexcellent in both tensile strength and elastic recovery, and having goodabrasion resistance, and a thermoplastic elastomer compositioncontaining the hydrogenated block copolymer.

BACKGROUND ART

Of the hydrogenated block copolymers, a hydrogenated styrene-basedthermoplastic elastomer is a thermoplastic elastomer excellent inweatherability, heat resistance, impact resistance, flexibility, andelastic recovery. A composition containing a hydrogenated blockcopolymer has been utilized in a wide variety of fields such asautomobile supplies, home appliances, medical supplies, constructionsupplies, toys, daily necessities, and miscellaneous goods because thecomposition imparts an excellent mechanical strength, flexibility,weatherability, ozone resistance, heat stability, and transparency. Insuch circumstances, a hydrogenated product of a block copolymer obtainedby copolymerizing a mixed monomer of isoprene and butadiene with styrenehas been proposed for the purpose of improving the low-temperaturecharacteristic, impact resistance, permanent set property, andmechanical strength of the hydrogenated styrene-based thermoplasticelastomer (see Patent Literature 1).

In addition, upon utilization of the excellent flexibility and elasticrecovery of the hydrogenated styrene-based thermoplastic elastomer, amethod involving mixing the elastomer with a plasticizer or variousthermoplastic resins before its use has been proposed. For example, thefollowing compositions have been proposed as such hydrogenatedstyrene-based thermoplastic elastomer composition: a composition formedof 20 to 80 wt % of an elastomer-like block copolymer, 5 to 60 wt % of aprocess oil, and 3 to 60 wt % of a vinylarene resin (see PatentLiterature 2); a composition containing 52 to 60 wt % of a block polymerhaving at least two polystyrene terminal blocks and a mid block formedof a hydrogenated polymerized diene whose vinyl content is 45 wt % orless, 19 to 28 wt % of an oil, and 13 to 22 wt % of a polystyrene (seePatent Literature 3); and a composition formed of 35 to 50 parts by massof a hydrogenated block copolymer having an aromatic vinyl content of 35to 45 mass % and a weight-average molecular weight of 70,000 to 120,000,30 to 50 parts by mass of a softener for a rubber, and 5 to 25 parts bymass of a polystyrene-based resin having a weight-average molecularweight of 100,000 to 400,000 (see Patent Literature 4).

CITATION LIST Patent Literature

-   [Patent Document 1] JP H03-188114 A-   [Patent Document 2] JP 2003-509565-   [Patent Document 3] JP 2003-509564-   [Patent Document 4] WO 2007/119390 A1

SUMMARY OF INVENTION Technical Problem

However, the hydrogenated block copolymer disclosed in Patent Document1, and the thermoplastic elastomer compositions disclosed in PatentDocument 2 to 4 have had room for further improvement because thecopolymer and compositions to be obtained are not necessarilysatisfactory in terms of both tensile strength and elastic recovery.

In addition, the hydrogenated styrene-based thermoplastic elastomer hasstarted to be used as an alternative material to soft vinyl chlorideused in, for example, automobile parts, home appliance parts, buildingmaterials, furniture, toys, sporting goods, and daily necessities, butthe elastomer has involved the following problem. The elastomer isinferior in abrasion resistance to the soft vinyl chloride.

In view of the foregoing, an object of the present invention is toprovide a hydrogenated block copolymer and a thermoplastic elastomercomposition each of which is excellent in both tensile strength andelastic recovery, and has good abrasion resistance.

Solution to Problem

The inventors of the present invention have made extensive studies tosolve the problems, and as a result, have found that, in a hydrogenatedblock copolymer obtained by hydrogenating a block copolymer having twoor more polymer blocks (a) each containing a structural unit derivedfrom an aromatic vinyl compound and one or more polymer blocks (b) eachcontaining structural units derived from isoprene and 1,3-butadiene(herein after sometimes simply referred to as “butadiene”), increasingthe ratio of the structural unit derived from butadiene to thestructural unit derived from isoprene in each polymer block (b)increases a tensile strength but tends to reduce elastic recovery, andhence the problems are not necessarily solved merely by controlling theratio between the structural unit derived from isoprene and thestructural unit derived from butadiene, and that the problems cannot besolved until the control is performed so that the hydrogenated blockcopolymer may have a specific crystallization peak temperature.

That is, the present invention relates to the following items (1) to(7).

(1) A hydrogenated block copolymer, which is obtained by hydrogenating ablock copolymer having two or more polymer blocks (a) each containing astructural unit derived from an aromatic vinyl compound and one or morepolymer blocks (b) each containing structural units derived fromisoprene and 1,3-butadiene, in which the hydrogenated block copolymerhas a crystallization peak temperature (Tc) defined as described belowof −3 to 15° C.:(crystallization peak temperature (Tc))

a peak top temperature of an exothermic peak observed when thetemperature of a sample is increased from 30° C. to 150° C. at a rate oftemperature increase of 10° C./min and then the sample is cooled to−100° C. at a rate of temperature decrease of 10° C./min, the peak toptemperature being measured with differential scanning calorimeter (DSC),is defined as the crystallization peak temperature (Tc).

(2) The hydrogenated block copolymer according to the above-mentioneditem (1), in which a mass ratio (isoprene/1,3-butadiene) of thestructural unit derived from isoprene to the structural unit derivedfrom 1,3-butadiene is 49.9/50.1 to 40.1/59.9.(3) The hydrogenated block copolymer according to the above-mentioneditem (1) or (2), in which the content of the polymer blocks (a) in thehydrogenated block copolymer (A) is 20 to 34 mass %.(4) A thermoplastic elastomer composition, comprising: the hydrogenatedblock copolymer (A) according to any one of the above-mentioned items(1) to (3); and a thermoplastic resin (B).(5) A thermoplastic elastomer composition, including: the hydrogenatedblock copolymer (A) according to any one of the above-mentioned items(1) to (3); a thermoplastic resin (B); and a softener for a rubber (C).(6) The thermoplastic elastomer composition according to theabove-mentioned item (5), in which in 100 parts by mass of the total ofthe hydrogenated block copolymer (A), the thermoplastic resin (B), andthe softener for a rubber (C), the content of the hydrogenated blockcopolymer (A) is 50 to 80 parts by mass, the content of thethermoplastic resin (B) is 5 to 30 parts by mass, and the content of thesoftener for a rubber (C) is 10 to 45 parts by mass.(7) The thermoplastic elastomer composition according to theabove-mentioned item (5) or (6), in which the thermoplastic resin (B)comprises a polystyrene-based resin (B′).

ADVANTAGEOUS EFFECTS OF INVENTION

According to one embodiment of the present invention, it is possible toprovide the hydrogenated block copolymer and the thermoplastic elastomercomposition containing the hydrogenated block copolymer, each of whichis excellent in both tensile strength and elastic recovery, and has goodabrasion resistance.

DESCRIPTION OF EMBODIMENTS Hydrogenated Block Copolymer (A)

A hydrogenated block copolymer (A) of the present invention is ahydrogenated block copolymer, which is obtained by hydrogenating a blockcopolymer having two or more polymer blocks (a) each containing astructural unit derived from an aromatic vinyl compound and one or morepolymer blocks (b) each containing structural units derived fromisoprene and 1,3-butadiene (herein after simply referred to asbutadiene), in which the hydrogenated block copolymer has acrystallization peak temperature (Tc) defined as described below of −3to 15° C.:

(crystallization peak temperature (Tc))

a peak top temperature of an exothermic peak observed when a temperatureof a sample is increased from 30° C. to 150° C. at a rate of temperatureincrease of 10° C./min and then the sample is cooled to −100° C. at arate of temperature decrease of 10° C./min, the peak top temperaturebeing measured with differential scanning calorimeter (DSC), is definedas the crystallization peak temperature (Tc).

The crystallization peak temperature in the hydrogenated block copolymer(A) needs to be −3 to 15° C. as described in the foregoing from theviewpoints of achieving compatibility between a tensile strength andelastic recovery, and obtaining good abrasion resistance, and ispreferably 0 to 14° C., more preferably 0 to 13° C., still morepreferably 2 to 13° C., particularly preferably 5 to 13° C., mostpreferably 5 to 11° C. When the crystallization peak temperature is lessthan −3° C., the hydrogenated block copolymer and a thermoplasticelastomer composition containing the copolymer are each poor in tensilestrength. When the temperature exceeds 15° C., the hydrogenated blockcopolymer and the thermoplastic elastomer composition are each poor inelastic recovery.

The polymer blocks (a) in the hydrogenated block copolymer (A) eachcontain preferably 50 mass % or more, more preferably 80 mass % or more,still more preferably 90 mass % or more, still further more preferably95 mass % or more, particularly preferably substantially 100 mass % ofthe structural unit derived from the aromatic vinyl compound. The phrase“derived from the aromatic vinyl compound” as used herein means that thestructural unit is a structural unit formed as a result of the additionpolymerization of the aromatic vinyl compound. Hereinafter, the term“derived” is used in the same meaning.

Examples of the aromatic vinyl compound include styrene,α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene,4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene,2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, vinyltoluene,1-vinylnaphthalene, and 2-vinylnaphthalene. Of those, styrene andα-methylstyrene are preferred, and styrene is more preferred. Each ofthe polymer blocks (a) may be constituted only of one kind of thosearomatic vinyl compounds, or may be constituted of two or more kindsthereof.

In addition, a structural unit except the structural unit derived fromthe aromatic vinyl compound in each of the polymer blocks (a) is, forexample, a structural unit derived from any other polymerizable monomersuch as a structural unit derived from a conjugated diene like isoprene,butadiene, 2,3-dimethyl-butadiene, 1,3-pentadiene, or 1,3-hexadiene.

The polymer block (b) in the hydrogenated block copolymer (A) containspreferably 50 mass % or more, more preferably 80 mass % or more, stillmore preferably 90 mass % or more, still further more preferably 95 mass% or more, particularly preferably substantially 100 mass % of thestructural units derived from isoprene and butadiene. The polymerizationform of the polymer block (b) is not particularly limited, and each ofrandom polymerization and block polymerization is permitted.

In addition, the mass ratio (isoprene/butadiene) of the structural unitderived from isoprene to the structural unit derived from butadiene inthe polymer block (b) is preferably 49.9/50.1 to 40.1/59.9, morepreferably 49/51 to 41/59, still more preferably 48/52 to 42/58 from theviewpoints of facilitating the achievement of the compatibility betweenthe tensile strength and the elastic recovery, and obtaining goodabrasion resistance. As described in Examples, the mass ratio is a valuedetermined by using the block copolymer before the hydrogenation from¹H-NMR spectrum. It should be noted that as long as the crystallizationpeak temperature falls within the specific range, the compatibilitybetween the tensile strength and the elastic recovery can be achievedirrespective of the mass ratio. On the other hand, as long as thecrystallization peak temperature deviates from the specific range, thecompatibility between the tensile strength and the elastic recoverycannot be achieved even when the mass ratio falls within the range.

In addition, the bonding form of isoprene and butadiene in the polymerblock (b), i.e., the so-called microstructure is not particularlylimited. For example, in the case of isoprene, any one of the bondingforms, i.e., a 1,2-bond (vinyl bond), a 3,4-bond (vinyl bond), and a1,4-bond can be adopted, and in the case of butadiene, any one of thebonding forms, i.e., the 1,2-bond (vinyl bond) and the 1,4-bond can beadopted. Only one kind of those bonding forms may be present, or two ormore kinds thereof may be present. In addition, each of those bondingforms may be present at any ratio, but from the viewpoint of the tensilestrength, the amount of the 1,4-bonds formed of the structural units ofisoprene and butadiene is preferably 60% or more, more preferably 80% ormore, still more preferably 85% or more, particularly preferably 90% ormore (more specifically 90 to 95%).

It should be noted that the amount of the 1,4-bonds in this descriptionis a value determined according to a method described in Examples byusing the block copolymer before the hydrogenation from ¹H-NMR spectrum.

In addition, examples of the structural unit except the structural unitsderived from isoprene and butadiene in the polymer block (b) includestructural units derived from other polymerizable monomers, such asstructural units derived from conjugated dienes such as2,3-dimethylbutadiene, 1,3-pentadiene, and 1,3-hexadiene, and structuralunits derived from aromatic vinyl compounds such as styrene,α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene,4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene,2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, vinyltoluene,1-vinylnaphthalene, and 2-vinylnaphthalene.

In the polymer block (b) in the hydrogenated block copolymer (A) of thepresent invention, preferably 50% or more, more preferably 80% or more,still more preferably 90% or more, still further more preferably 95% ormore, particularly preferably 96 to 100% of carbon-carbon double bondsderived from isoprene and butadiene are hydrogenated from the viewpointsof heat resistance, weatherability, and the tensile strength.

It should be noted that the hydrogenation ratio is a value determinedfrom measured values obtained by measuring the contents of thecarbon-carbon double bonds derived from isoprene and butadiene in thepolymer block (b) before and after the hydrogenation with ¹H-NMRspectrum.

The hydrogenation of the carbon-carbon double bonds causes the polymerblock (b) to have crystallinity. The crystallization peak temperature ofthe hydrogenated block copolymer (A) can be set within the specificrange by comprehensively adjusting, for example, the content ofbutadiene in the polymer block (b), the randomness of anisoprene-butadiene chain, the microstructure, and the hydrogenationratio.

In general, the crystallinity is observed when about twelve methylenegroups are linearly linked. In other words, the crystallinity isobserved when a completely hydrogenated chain in which three butadienemolecules are linked through 1,4-bonds is present. In contrast, when a1,4-bonded polyisoprene is completely hydrogenated, the polyisoprene isof an ethylene-propylene alternating copolymer structure and hence doesnot have crystallinity. In view of the foregoing, to increase thecontent of butadiene, to increase a butadiene chain, to increase theamount of the 1,4-bonds, and to increase the hydrogenation ratio areeach effective in raising the crystallization peak temperature, and toincrease the content of isoprene, to raise the randomness of theisoprene-butadiene chain, to reduce the amount of the 1,4-bonds, and toreduce the hydrogenation ratio are each effective in lowering thecrystallization peak temperature.

Further, the crystallization peak temperature of the hydrogenated blockcopolymer (A) is affected by a temperature at the time of apolymerization reaction in the polymer block (b) and the rate at whichisoprene or butadiene is supplied. Accordingly, those values need to beappropriately adjusted for obtaining a desired crystallization peaktemperature. In other words, the crystallization peak temperature of thehydrogenated block copolymer (A) can be controlled to the specific valueby controlling the temperature at the time of the polymerizationreaction, the mass ratio between isoprene and butadiene, and the ratesat which isoprene and butadiene are supplied.

The content of the polymer blocks (a) in the hydrogenated blockcopolymer (A) is preferably 10 to 34 mass %, more preferably 12 to 34mass %, still more preferably 15 to 34 mass %, still further morepreferably 20 to 34 mass %, particularly preferably 25 to 34 mass %,most preferably 25 to 33 mass %. When the content of the polymer blocks(a) in the hydrogenated block copolymer (A) is 10 mass % or more, thehydrogenated block copolymer and the thermoplastic elastomer compositionare each excellent in tensile strength. On the other hand, when thecontent is 34 mass % or less, the copolymer and the composition are eachexcellent in elastic recovery.

It should be noted that the content of the polymer blocks (a) in thehydrogenated block copolymer (A) is determined from ¹H-NMR spectrumafter the hydrogenation.

The bonding mode of the polymer blocks (a) and polymer block (b) in thehydrogenated block copolymer (A) may be any one of a linear mode, abranched mode, a radial mode, and an arbitrary combination thereof.

For example, when the polymer block (a) is represented by “A” and thepolymer block (b) is represented by “B,” a triblock copolymerrepresented by “A-B-A,” a tetra block copolymer represented by“A-B-A-B,” a penta block copolymer represented by “A-B-A-B-A” or“B-A-B-A-B,” and a (A-B)nX-type copolymer (where X represents a couplingagent residue and n represents an integer of 2 or more), and the likeare given. Of those, a triblock copolymer represented by “A-B-A” or atetra block copolymer represented by “A-B-A-B” is preferred as thehydrogenated block copolymer (A) in terms of ease of production, and atriblock copolymer represented by “A-B-A” is more preferably used.

The weight-average molecular weight (Mw) of the hydrogenated blockcopolymer (A) is preferably 50,000 to 500,000, more preferably 60,000 to400,000, still more preferably 65,000 to 300,000, particularlypreferably 70,000 to 115,000. When the weight-average molecular weightof the hydrogenated block copolymer (A) is 50,000 or more, thehydrogenated block copolymer (A) and the thermoplastic elastomercomposition are each excellent in tensile strength. When theweight-average molecular weight is 500,000 or less, the hydrogenatedblock copolymer (A) and the thermoplastic elastomer composition eachhave good moldability.

The molecular weight distribution (Mw/Mn) of the hydrogenated blockcopolymer (A) is preferably 1.5 or less, more preferably 1.01 to 1.5,still more preferably 1.01 to 1.3, still further more preferably 1.01 to1.2, particularly preferably 1.01 to 1.1, most preferably 1.01 to 1.05.

It should be noted that the weight-average molecular weight and themolecular weight distribution are values in terms of standardpolystyrene determined by gel permeation chromatography (GPC)measurement.

In addition, the glass transition temperature (Tg) of the hydrogenatedblock copolymer (A) is preferably −60 to −30° C., more preferably −60 to−40° C., still more preferably −55 to −45° C. Further, the crystalmelting heat quantity of the hydrogenated block copolymer (A) ispreferably 15 to 30 mJ/mg, more preferably 15 to 25 mJ/mg, still morepreferably 17 to 25 mJ/mg. The glass transition temperature (Tg) and thecrystal melting heat quantity are values measured according to methodsdescribed in Examples with differential scanning calorimeter (DSC).

In addition, the tensile strength of the hydrogenated block copolymer(A) measured according to a method described in Examples is about 40 to45 MPa, and its elastic recovery measured according to a methoddescribed in Examples is about 0.3 to 0.5.

It should be noted that the hydrogenated block copolymer (A) may haveone or two or more kinds of functional groups such as a carboxyl group,a hydroxyl group, an acid anhydride group, an amino group, and an epoxygroup in its molecular chain and/or a molecular terminal thereof as longas an effect of the present invention is not remarkably impaired.

(Method of Producing Hydrogenated Block Copolymer (A))

The hydrogenated block copolymer (A) can be produced by, for example, ananionic polymerization method. Specifically, the copolymer can beproduced by: performing a polymerization reaction according to, forexample, (1) a method involving sequentially polymerizing the aromaticvinyl compound, and isoprene and butadiene with an alkyllithium compoundas an initiator, (2) a method involving sequentially polymerizing thearomatic vinyl compound, and isoprene and butadiene with thealkyllithium compound as an initiator, and then adding a coupling agentto couple the resultant, or (3) a method involving sequentiallypolymerizing isoprene and butadiene, and then the aromatic vinylcompound with a dilithium compound as an initiator; and then performinga hydrogenation reaction.

It should be noted that isoprene and butadiene may be separatelysupplied to a reactor at the same time to be turned into a mixture inthe reactor, isoprene and butadiene may be supplied to the reactor in astate of being mixed in advance, or both the former method and thelatter method may be adopted.

Examples of the alkyl lithium compound include methyllithium,ethyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, andpentyllithium.

Examples of the coupling agent include: divinylbenzene; polyvalent epoxycompounds such as an epoxidized 1,2-polybutadiene, epoxidized soybeanoil, and 1,3-bis(N,N-glycidylaminomethyl)cyclohexane; halogen compoundssuch as dimethyldichlorosilane, dimethyldibromosilane, trichlorosilane,methyltrichlorosilane, tetrachlorosilane, and tetrachlorotin; estercompounds such as methyl benzoate, ethyl benzoate, phenyl benzoate,diethyl oxalate, diethyl malonate, diethyl adipate, dioctyl adipate,dimethyl phthalate, diethyl phthalate, dimethyl isophthalate, anddimethyl terephthalate; carbonic acid ester compounds such as dimethylcarbonate, diethyl carbonate, and carbonate diphenyl; and alkoxysilanecompounds such as dimethyldimethoxysilane, methyltrimethoxysilane,methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane,bis(trimethoxysilyl)hexane, and bis(triethoxysilyl)ethane.

In addition, examples of the dilithium compound includenaphthalenedilithium and dilithiohexylbenzene.

The polymerization reaction is preferably performed in the presence of asolvent. The solvent is not particularly limited as long as the solventis inert to the initiator and does not adversely affect the reaction.Examples thereof include: saturated aliphatic hydrocarbons such ashexane, cyclohexane, heptane, octane, and decane; and aromatichydrocarbons such as toluene, benzene, and xylene. In addition, thepolymerization reaction is performed at preferably 0 to 100° C. (morepreferably 30 to 90° C., still more preferably 40 to 80° C.,particularly preferably 50 to 80° C.) for preferably 0.5 to 50 hours inordinary cases from the viewpoint of controlling the microstructure.

In addition, in the polymerization reaction, a Lewis base may be used asa cocatalyst. Examples of the Lewis base include: ethers such asdimethyl ether, diethyl ether, and tetra hydrofuran; glycol ethers suchas ethylene glycol dimethyl ether and diethylene glycol dimethyl ether;and amines such as triethylamine, N,N,N′,N′-tetramethylethylenediamine,and N-methylmorpholine. One kind of those Lewis bases may be used alone,or two or more kinds thereof may be used in combination.

The hydrogenation reaction may be performed subsequently to thepolymerization reaction or the block copolymer may be temporarilyisolated after the polymerization reaction before the hydrogenationreaction is performed.

When the block copolymer is temporarily isolated after thepolymerization reaction, the block copolymer can be isolated byperforming the polymerization according to the method described aboveand then pouring the resultant polymerization reaction liquid into apoor solvent for the block copolymer such as methanol to coagulate theblock copolymer, or pouring the polymerization reaction liquid into hotwater together with steam to remove the solvent through azeotropy (steamstripping) and then drying the residue.

The hydrogenation reaction of the block copolymer can be performed bysubjecting the block copolymer to a reaction in the presence of ahydrogenation catalyst such as: Raney nickel; a heterogeneous catalystobtained by causing a support such as carbon, alumina, or diatomaceousearth to carry a metal such as platinum (Pt), palladium (Pd), ruthenium(Ru), rhodium (Rh), or nickel (Ni); a Ziegler type catalyst formed of acombination of a transition metal compound (e.g., nickel octylate,nickel naphthenate, nickel acetylacetonate, cobalt octylate, cobaltnaphthenate, or cobalt acetylacetonate) and an organic aluminum compoundsuch as triethylaluminum or triisobutylaluminum, an organic lithiumcompound, or the like; or a metallocene-based catalyst formed of acombination of bis(cyclopentadienyl) compound of a transition metal suchas titanium, zirconium, or hafnium and an organic metal compoundincluding lithium, sodium, potassium, aluminum, zinc, magnesium, or thelike generally preferably under the conditions of a reaction temperatureof 20 to 200° C. and a hydrogen pressure 0.1 to 20 MPa for 0.1 to 100hours.

When the polymerization reaction and the hydrogenation reaction arecontinuously performed, the isolation of the hydrogenated blockcopolymer (A) can be performed by pouring the hydrogenation reactionliquid into a poor solvent for the hydrogenated block copolymer (A) suchas methanol to coagulate the hydrogenated block copolymer (A), orpouring the hydrogenation reaction liquid into hot water together withsteam to remove the solvent by azeotropy (steam stripping) and thendrying the residue.

According to the present invention, a hydrogenated block copolymerhaving a tensile strength measured according to the method described inExamples of about 38 to 44 MPa can be obtained. In addition, ahydrogenated block copolymer having an elastic recovery [f(return100%)/f(outward 100%)] determined according to the method described inExamples of about 0.33 to 0.55 can be obtained. Further, thehydrogenated block copolymer of the present invention has an abrasionresistance measured according to a method described in Examples of about140 to 147 mm³, in other words, the abrasion resistance is good.

The present invention provides a thermoplastic elastomer compositioncontaining, for example, the hydrogenated block copolymer (A), athermoplastic resin (B), and as required, a softener for a rubber (C) aswell. In the thermoplastic elastomer composition, one kind of thehydrogenated block copolymers (A) may be used alone, or two or morekinds thereof may be used in combination.

(Thermoplastic Resin (B))

Examples of the thermoplastic resin (B) to be incorporated into thethermoplastic elastomer composition of the present invention include apolystyrene-based resin (B′), a polyethylene-based resin, apolypropylene-based resin, an acrylic resin, a polyphenylene ether-basedresin, a polycarbonate-based resin, a polyvinyl acetate-based resin, apolyester-based resin, a polyamide-based resin, and a polyvinylchloride-based resin.

Examples of the polystyrene-based resin (B′) can include a polystyrene(general purpose polystyrene (GPPS), high impact polystyrene (HIPS)), apoly-o-methylstyrene, a poly-p-methylstyrene, a polydimethylstyrene, apoly-m-ethylstyrene, a polychlorostyrene, a polyisopropylstyrene, apoly-t-butylstyrene, a poly-α-methylstyrene, a polyethylvinyltoluene, astyrene-maleimide copolymer, a styrene-N-phenylmaleimide copolymer, astyrene-N-phenylmaleimide-acrylonitrile copolymer, astyrene-N-phenylmaleimide-methyl methacrylate copolymer, astyrene-N-phenylmaleimide-butyl acrylate copolymer, rubber-reinforcedhigh impact polystyrene, an acrylonitrile-styrene copolymer (AS resin),an acrylonitrile-butadiene-styrene copolymer (ABS resin), anacrylonitrile-ethylene-propylene rubber-reinforced styrene copolymer(AES resin), an acrylonitrile-polyacrylic acid ester rubber-reinforcedstyrene copolymer (AAS resin), a methyl methacrylate-styrene copolymer(MS resin), and a methyl methacrylate-butadiene-styrene copolymer (MBSresin).

Examples of the polyethylene-based resin can include: homopolymers ofethylene such as a high-density polyethylene and a low-densitypolyethylene; and copolymers of ethylene such as ethylene-α-olefincopolymers such as an ethylene-propylene copolymer, an ethylene-1-butenecopolymer, an ethylene-1-hexene copolymer, an ethylene-1-heptenecopolymer, an ethylene-1-octene copolymer, anethylene-4-methyl-1-pentene copolymer, an ethylene-1-nonene copolymer,and an ethylene-1-decene copolymer, an ethylene-vinyl acetate copolymer,an ethylene-acrylic acid copolymer, an ethylene-acrylic acid estercopolymer, an ethylene-methacrylic acid copolymer, and anethylene-methacrylic acid ester copolymer, or resins obtained bymodifying these copolymers with maleic anhydride or the like.

Examples of the polypropylene-based resin can include ahomopolypropylene, a random polypropylene, and a block polypropylene.Examples of the polyester-based resin include a polyethyleneterephthalate, a polybutylene terephthalate, a polylactic acid, and apolycaprolactone. Examples of the polyamide-based resin include apolyamide 6, a polyamide 6/6, a polyamide 6/10, a polyamide 11, apolyamide 12, a polyamide 6/12, a polyhexamethylenediamineterephthalamide, a polyhexamethylenediamine isophthalamide, and a xylenegroup-containing polyamide.

One kind of the thermoplastic resins (B) may be used alone, or two ormore kinds thereof may be used in combination. Of those, apolystyrene-based resin (B′) is suitably used.

The weight-average molecular weight of the polystyrene-based resin (B′)to be suitably used as the thermoplastic resin (B) falls within therange of 100,000 to 400,000, preferably falls within the range of120,000 to 350,000, and more preferably falls within the range of150,000 to 300,000. When the weight-average molecular weight of thepolystyrene-based resin (B′) is less than 100,000, the stress relaxationproperty of the thermoplastic elastomer composition to be obtainedreduces. When the weight-average molecular weight exceeds 400,000, themoldability of the thermoplastic elastomer composition may reduce.

(Softener for a Rubber (C))

Examples of the softener for a rubber (C) to be incorporated into thethermoplastic elastomer composition of the present invention as requiredinclude: mineral oils such as paraffin-based process oil andnaphthene-based process oil; plant oils such as peanut oil and rosin;phosphoric acid esters; low-molecular-weight polyethylene glycol; liquidparaffin; and synthetic oils such as low-molecular-weight polyethylene,an ethylene-α-olefin co-oligomer, liquid polybutene, liquid polyisopreneor a hydrogenated product thereof, and liquid polybutadiene or ahydrogenated product thereof. Of those, paraffin-based oil such asparaffin-based process oil or liquid paraffin is suitably used. As theparaffin-based oil, a paraffin-based oil having a kinetic viscosity at40° C. of 20 to 1,500 mm²/s is preferred, a paraffin-based oil having adynamic viscosity of 50 to 1,000 mm²/s is more preferred, and aparaffin-based oil having a kinetic viscosity of 70 to 500 mm²/s isstill more preferred. One kind of those oils may be used alone, or twoor more kinds thereof may be used in combination.

The thermoplastic elastomer composition of the present invention ispreferably such that in 100 parts by mass of the total of thehydrogenated block copolymer (A), the thermoplastic resin (B), and thesoftener for a rubber (C), the content of the hydrogenated blockcopolymer (A) is 50 to 80 parts by mass, the content of thethermoplastic resin (B) is 5 to 30 parts by mass, and the content of thesoftener for a rubber (C) is 10 to 45 parts by mass from the followingviewpoint: its tensile strength and elastic recovery can be improved ina balanced manner. It is more preferred that in 100 parts by mass of thetotal of the hydrogenated block copolymer (A), the thermoplastic resin(B), and the softener for a rubber (C), the content of the hydrogenatedblock copolymer (A) be 55 to 75 parts by mass, the content of thethermoplastic resin (B) be 5 to 20 parts by mass, and the content of thesoftener for a rubber (C) be 15 to 40 parts by mass.

When the content of the hydrogenated block copolymer (A) is 50 parts bymass or more, the thermoplastic elastomer composition to be obtained isexcellent in tensile strength. On the other hand, when the content is 80parts by mass or less, the moldability of the thermoplastic elastomercomposition to be obtained becomes good.

In addition, when the content of the thermoplastic resin (B) is 5 partsby mass or more, the thermoplastic elastomer composition to be obtainedis excellent in tensile strength. On the other hand, when the content is30 parts by mass or less, the moldability of the thermoplastic elastomercomposition becomes good.

In addition, when the content of the softener for a rubber (C) is 10parts by mass or more, the moldability of the thermoplastic elastomercomposition to be obtained becomes good. On the other hand, when thecontent is 45 parts by mass or less, the thermoplastic elastomercomposition to be obtained is excellent in tensile strength.

The thermoplastic elastomer composition of the present invention can beblended with any other component in addition to the above-mentionedcomponents depending on purposes as long as the effect of the presentinvention is not remarkably impaired.

Examples of the other component can include: various additives such as afiller, an antioxidant, a heat stabilizer, a light stabilizer, a UVabsorber, a neutralizer, a lubricant, an anti-fogging agent, ananti-blocking agent, a colorant, a flame retardant, an antistatic agent,a crosslinking agent, a conductivity-imparting agent, an antimicrobialagent, and a mildewproofing agent; a thermoplastic resin except theabove-mentioned components; and an elastomer except the essentialcomponents. In addition, one kind arbitrarily selected from thosecomponents may be used alone, or two or more kinds thereof may be usedin combination.

The thermoplastic elastomer composition of the present invention can beproduced by mixing the hydrogenated block copolymer (A), thethermoplastic resin (B), and as required, the softener for a rubber (C),and the other component to be blended as required. A conventional methodcan be adopted as the mixing method. For example, it is recommended tomix the components homogeneously using a mixing device such as ahigh-speed mixer, a ribbon blender, or a V-shaped blender, and then meltand knead the mixture using a kneading device such as a mixing roll, akneader, a Banbury mixer, a Brabender mixer, or a mono-screw ortwin-screw extruder. In general, the kneading is performed at 120 to280° C.

The tensile strength of the thermoplastic elastomer composition thusobtained measured according to the method described in Examples is about21.5 to 32 MPa, and its elastic recovery [f(return 100%)/f(outward100%)] measured according to the method described in Examples is about0.7 to 0.85.

Various molded articles can be produced by subjecting the resultantthermoplastic elastomer composition to general molding in accordancewith various forms.

For example, when the resultant thermoplastic elastomer composition ismolded into a film such as an elastic film, the film may be a monolayerfilm using the thermoplastic elastomer composition of the presentinvention alone, or may be a multilayer film obtained by extruding thecomposition together with a thermoplastic resin such as a polyethylene.Known molding technologies such as T-die film molding involving using amonolayer or laminated die, extrusion laminate molding, and co-extrusionmolding can each be adopted as a method of producing the monolayer orlaminated film. The thickness of the film preferably falls within therange of 15 to 200 μm in ordinary cases.

EXAMPLES

Hereinafter, the present invention is described in detail by way ofexamples and comparative examples. However, the present invention is notlimited to these examples. It should be noted that in each of thefollowing examples and comparative examples, the physical properties ofa hydrogenated block copolymer and a thermoplastic elastomer compositionwere evaluated by the following methods.

(1) Methods of Measuring Crystallization Peak Temperature, GlassTransition Temperature, and Crystal Melting Heat Quantity

A crystallization peak temperature was determined from an exothermicpeak observed in a temperature decrease process as the following secondstep with differential scanning calorimeter (DSC), and a glasstransition temperature and a crystal melting heat quantity weredetermined from an endothermic peak observed in a temperature increaseprocess as the following third step with the DSC.

Apparatus: DSC6200 (manufactured by Seiko Instruments Inc.)Rate of temperature increase: 10° C./minRate of temperature decrease: 10° C./minNitrogen flow rate: 40 ml/minTemperature profile:

1st: 30° C.→150° C. (kept for 5 minutes)

2nd: 150° C.→−100° C. (kept for 5 minutes)

3rd: −100° C.→150° C.

(2) Methods of Measuring Hydrogenation Ratio, Styrene Content, Amount of1,4-Bonds, and Mass Ratio of Structural Unit Derived from Isoprene toStructural Unit Derived from Butadiene

Each of the values was determined from ¹H-NMR spectrum. It should benoted that the mass ratio of a structural unit derived from isoprene toa structural unit derived from butadiene was measured with a blockcopolymer before hydrogenation.

Apparatus: JNM-Lambda 500 (manufactured by JEOL Ltd.)Solvent: deuterated chloroformMeasurement temperature: 50° C.

(3) Method of Measuring Weight-Average Molecular Weight (Mw) andMolecular Weight Distribution (Mw/Mn)

A weight-average molecular weight (Mw) and a molecular weightdistribution (Mw/Mn) were determined in terms of standard polystyrene bygel permeation chromatography (GPC).

Apparatus: GPC-8020 (manufactured by TOSOH CORPORATION)Solvent: tetra hydrofuranMeasurement temperature: 40° C.Flow rate: 1 ml/minInjection volume: 150 μl, Concentration: 5 mg/10 cc (hydrogenated blockcopolymer/THF)

(4) Method of Measuring Tensile Strength

Each of the hydrogenated block copolymers and thermoplastic elastomercompositions obtained in Examples and Comparative Examples was subjectedto press molding at 230° C. to provide a sheet having a thickness ofabout 0.6 mm. A dumbbell test piece (dumbbell No. 3 shape) specified inJIS K6251 was produced from the resultant sheet, and then its tensilestrength was measured with a tensile tester “5566 Model” manufactured byInstron at a measurement temperature of 23° C. and a tension speed of500 mm/min.

(5) Method of Measuring Elastic Recovery Each of the hydrogenated blockcopolymers and thermoplastic elastomer compositions obtained in Examplesand Comparative Examples was subjected to press molding at 230° C. toprovide a sheet having a thickness of about 0.6 mm. A strip-shaped testpiece having a width of 25 mm and a length of 150 mm was punched out ofthe resultant sheet and defined as a test piece. With reference to the“two-cycle hysteresis test” described in the paragraphs [0125] and[0126] of JP 2003-509565 W, the test piece was stretched by 200% with atensile tester “5566 Model” manufactured by Instron at a chuck-to-chuckdistance of 50 mm, a test temperature of 23° C., and a testing speed of500 mm/min, held in the state for 30 seconds, and then contracted to 0%at a testing speed of 500 mm/min, followed by the measurement of a 100%stretching stress in an advancing direction [f(outward 100%)] and a 100%stretching stress in a returning direction [f(return 100%)] at thattime. A ratio between those stresses was determined as represented bythe following equation and defined as an indicator of elastic recovery.It should be noted that when the following value is closer to 1, theelastic recovery is more excellent.

Elastic recovery=f(return 100%)/f(outward 100%)

(6) Method of Measuring DIN Abrasion Volume

Each of the hydrogenated block copolymers obtained in Examples andComparative Examples was subjected to press molding at 230° C. toprovide a sheet having a thickness of about 1 mm. Nine discs each havinga diameter of 16 mm were punched out of the resultant sheet andsuperimposed on one another, and then the resultant was subjected topress molding at 230° C. again to produce a disc-shaped test piecespecified in JIS K6264 having a diameter of 16 mm and a thickness of 8mm. The test piece was evaluated for its abrasion resistance bymeasuring its abrasion volume (unit: mm³) with a DIN-abrasion tester(manufactured by Toyo Seiki Seisaku-Sho, Ltd.). It should be noted thatwhen the value is smaller, the abrasion resistance is more excellent.

Example 1

3,000 Milliliters of cyclohexane as a solvent and 9.2 ml ofsec-butyllithium (cyclohexane solution) having a concentration of 10.5mass % as an initiator were loaded into a pressure-resistant containerthat had been replaced with nitrogen and dried, and then the temperatureof the mixture was increased to 60° C. After that, 100 ml of styrenewere added to the mixture and then the whole was polymerized for 60minutes.

After that, at the temperature, 4.3 ml of isoprene and 5.7 ml ofbutadiene were added to the resultant at substantially the same time inone stroke, and then the mixture was subjected to a reaction. After theresultant had been left to stand for 3.8 minutes, the same amounts ofisoprene and butadiene as those described in the foregoing were added tothe resultant at substantially the same time in one stroke, and then themixture was subjected to a reaction. The foregoing operations wererepeatedly performed to finally add a total of 265 ml of isoprene and atotal of 360 ml of butadiene. After that, a reaction was forced for anadditional 90 minutes.

Further, at the temperature, 100 ml of styrene were added to theresultant and then the mixture was polymerized for 60 minutes. Afterthat, the polymerization was stopped with 0.52 ml of methanol. Thus, apolymerization reaction liquid containing a block copolymer wasobtained.

29.3 Grams of palladium on carbon (palladium-carrying amount: 5 mass %)as a hydrogenation catalyst were added to the reaction mixed liquid, andthen a hydrogenation reaction was performed at a hydrogen pressure of 2MPa and 150° C. for 10 hours. After the resultant had been left standingto cool and the pressure had been discharged, the palladium on carbonwas removed by filtration, and then the filtrate was concentrated andvacuum-dried to provide a hydrogenated block copolymer (A-1).

Table 1 shows the results of the measurement of the physical propertiesof the resultant hydrogenated block copolymer (A-1).

Example 2

3,000 Milliliters of cyclohexane as a solvent and 9.2 ml ofsec-butyllithium (cyclohexane solution) having a concentration of 10.5mass % as an initiator were loaded into a pressure-resistant containerthat had been replaced with nitrogen and dried, and then the temperatureof the mixture was increased to 60° C. After that, 100 ml of styrenewere added to the mixture and then the whole was polymerized for 60minutes.

After that, at the temperature, 4.1 ml of isoprene and 5.9 ml ofbutadiene were added to the resultant at substantially the same time inone stroke, and then the mixture was subjected to a reaction. After theresultant had been left to stand for 2.9 minutes, the same amounts ofisoprene and butadiene as those described in the foregoing were added tothe resultant at substantially the same time in one stroke, and then themixture was subjected to a reaction. The foregoing operations wererepeatedly performed to finally add a total of 256 ml of isoprene and atotal of 369 ml of butadiene. After that, a reaction was forced for anadditional 90 minutes.

Further, at the temperature, 100 ml of styrene were added to theresultant and then the mixture was polymerized for 60 minutes. Afterthat, the polymerization was stopped with 0.52 ml of methanol. Thus, apolymerization reaction liquid containing a block copolymer wasobtained.

29.3 Grams of palladium on carbon (palladium-carrying amount: 5 mass %)as a hydrogenation catalyst were added to the reaction mixed liquid, andthen a hydrogenation reaction was performed at a hydrogen pressure of 2MPa and 150° C. for 10 hours. After the resultant had been left standingto cool and the pressure had been discharged, the palladium on carbonwas removed by filtration, and then the filtrate was concentrated andvacuum-dried to provide a hydrogenated block copolymer (A-2).

Table 1 shows the results of the measurement of the physical propertiesof the resultant hydrogenated block copolymer (A-2).

Example 3

3,000 Milliliters of cyclohexane as a solvent and 8.2 ml ofsec-butyllithium (cyclohexane solution) having a concentration of 10.5mass % as an initiator were loaded into a pressure-resistant containerthat had been replaced with nitrogen and dried, and then the temperatureof the mixture was increased to 55° C. After that, 100 ml of styrenewere added to the mixture and then the whole was polymerized for 60minutes.

After that, at the temperature, 4.5 ml of isoprene and 5.5 ml ofbutadiene were added to the resultant at substantially the same time inone stroke, and then the mixture was subjected to a reaction. After theresultant had been left to stand for 2.1 minutes, the same amounts ofisoprene and butadiene as those described in the foregoing were added tothe resultant at substantially the same time in one stroke, and then themixture was subjected to a reaction. The foregoing operations wererepeatedly performed to finally add a total of 255 ml of isoprene and atotal of 313 ml of butadiene. After that, a reaction was forced for anadditional 90 minutes.

Further, at the temperature, 100 ml of styrene were added to theresultant and then the mixture was polymerized for 60 minutes. Afterthat, the polymerization was stopped with 0.46 ml of methanol. Thus, apolymerization reaction liquid containing a block copolymer wasobtained.

27.4 Grams of palladium on carbon (palladium-carrying amount: 5 mass %)as a hydrogenation catalyst were added to the reaction mixed liquid, andthen a hydrogenation reaction was performed at a hydrogen pressure of 2MPa and 150° C. for 10 hours. After the resultant had been left standingto cool and the pressure had been discharged, the palladium on carbonwas removed by filtration, and then the filtrate was concentrated andvacuum-dried to provide a hydrogenated block copolymer (A-3).

Table 1 shows the results of the measurement of the physical propertiesof the resultant hydrogenated block copolymer (A-3).

Example 4

3,000 Milliliters of cyclohexane as a solvent and 9.5 ml ofsec-butyllithium (cyclohexane solution) having a concentration of 10.5mass % as an initiator were loaded into a pressure-resistant containerthat had been replaced with nitrogen and dried, and then the temperatureof the mixture was increased to 55° C. After that, 100 ml of styrenewere added to the mixture and then the whole was polymerized for 60minutes.

After that, at the temperature, 4.3 ml of isoprene and 5.7 ml ofbutadiene were added to the resultant at substantially the same time inone stroke, and then the mixture was subjected to a reaction. After theresultant had been left to stand for 1.6 minutes, the same amounts ofisoprene and butadiene as those described in the foregoing were added tothe resultant at substantially the same time in one stroke, and then themixture was subjected to a reaction. The foregoing operations wererepeatedly performed to finally add a total of 268 ml of isoprene and atotal of 356 ml of butadiene. After that, a reaction was forced for anadditional 90 minutes.

Further, at the temperature, 100 ml of styrene were added to theresultant and then the mixture was polymerized for 60 minutes. Afterthat, the polymerization was stopped with 0.54 ml of methanol. Thus, apolymerization reaction liquid containing a block copolymer wasobtained.

29.3 Grams of palladium on carbon (palladium-carrying amount: 5 mass %)as a hydrogenation catalyst were added to the reaction mixed liquid, andthen a hydrogenation reaction was performed at a hydrogen pressure of 2MPa and 150° C. for 10 hours. After the resultant had been left standingto cool and the pressure had been discharged, the palladium on carbonwas removed by filtration, and then the filtrate was concentrated andvacuum-dried to provide a hydrogenated block copolymer (A-4).

Table 1 shows the results of the measurement of the physical propertiesof the resultant hydrogenated block copolymer (A-4).

Example 5

3,000 Milliliters of cyclohexane as a solvent and 9.3 ml ofsec-butyllithium (cyclohexane solution) having a concentration of 10.5mass % as an initiator were loaded into a pressure-resistant containerthat had been replaced with nitrogen and dried, and then the temperatureof the mixture was increased to 55° C. After that, 100 ml of styrenewere added to the mixture and then the whole was polymerized for 60minutes.

After that, at the temperature, 5.0 ml of isoprene and 5.0 ml ofbutadiene were added to the resultant at substantially the same time inone stroke, and then the mixture was subjected to a reaction. After theresultant had been left to stand for 2.4 minutes, the same amounts ofisoprene and butadiene as those described in the foregoing were added tothe resultant at substantially the same time in one stroke, and then themixture was subjected to a reaction. The foregoing operations wererepeatedly performed to finally add a total of 310 ml of isoprene and atotal of 310 ml of butadiene. After that, a reaction was forced for anadditional 90 minutes.

Further, at the temperature, 100 ml of styrene were added to theresultant and then the mixture was polymerized for 60 minutes. Afterthat, the polymerization was stopped with 0.52 ml of methanol. Thus, apolymerization reaction liquid containing a block copolymer wasobtained.

29.3 Grams of palladium on carbon (palladium-carrying amount: 5 mass %)as a hydrogenation catalyst were added to the reaction mixed liquid, andthen a hydrogenation reaction was performed at a hydrogen pressure of 2MPa and 150° C. for 10 hours. After the resultant had been left standingto cool and the pressure had been discharged, the palladium on carbonwas removed by filtration, and then the filtrate was concentrated andvacuum-dried to provide a hydrogenated block copolymer (A-5).

Table 1 shows the results of the measurement of the physical propertiesof the resultant hydrogenated block copolymer (A-5).

Comparative Example 1

3,000 Milliliters of cyclohexane as a solvent and 9.2 ml ofsec-butyllithium (cyclohexane solution) having a concentration of 10.5mass % as an initiator were loaded into a pressure-resistant containerthat had been replaced with nitrogen and dried, and then the temperatureof the mixture was increased to 60° C. After that, 100 ml of styrenewere added to the mixture and then the whole was polymerized for 60minutes.

After that, at the temperature, 5.4 ml of isoprene and 4.6 ml ofbutadiene were added to the resultant at substantially the same time inone stroke, and then the mixture was subjected to a reaction. After theresultant had been left to stand for 2.1 minutes, the same amounts ofisoprene and butadiene as those described in the foregoing were added tothe resultant at substantially the same time in one stroke, and then themixture was subjected to a reaction. The foregoing operations wererepeatedly performed to finally add a total of 334 ml of isoprene and atotal of 284 ml of butadiene. After that, a reaction was forced for anadditional 90 minutes.

Further, at the temperature, 100 ml of styrene were added to theresultant and then the mixture was polymerized for 60 minutes. Afterthat, the polymerization was stopped with 0.52 ml of methanol. Thus, apolymerization reaction liquid containing a block copolymer wasobtained.

29.3 Grams of palladium on carbon (palladium-carrying amount: 5 mass %)as a hydrogenation catalyst were added to the reaction mixed liquid, andthen a hydrogenation reaction was performed at a hydrogen pressure of 2MPa and 150° C. for 10 hours. After the resultant had been left standingto cool and the pressure had been discharged, the palladium on carbonwas removed by filtration, and then the filtrate was concentrated andvacuum-dried to provide a hydrogenated block copolymer (A′-1).

Table 1 shows the results of the measurement of the physical propertiesof the resultant hydrogenated block copolymer (A′-1).

Comparative Example 2

3,000 Milliliters of cyclohexane as a solvent and 9.2 ml ofsec-butyllithium (cyclohexane solution) having a concentration of 10.5mass % as an initiator were loaded into a pressure-resistant containerthat had been replaced with nitrogen and dried, and then the temperatureof the mixture was increased to 55° C. After that, 100 ml of styrenewere added to the mixture and then the whole was polymerized for 60minutes.

After that, at the temperature, 3.8 ml of isoprene and 6.2 ml ofbutadiene were added to the resultant at substantially the same time inone stroke, and then the mixture was subjected to a reaction. After theresultant had been left to stand for 3.8 minutes, the same amounts ofisoprene and butadiene as those described in the foregoing were added tothe resultant at substantially the same time in one stroke, and then themixture was subjected to a reaction. The foregoing operations wererepeatedly performed to finally add a total of 238 ml of isoprene and atotal of 389 ml of butadiene. After that, a reaction was forced for anadditional 90 minutes.

Further, at the temperature, 100 ml of styrene were added to theresultant and then the mixture was polymerized for 60 minutes. Afterthat, the polymerization was stopped with 0.52 ml of methanol. Thus, apolymerization reaction liquid containing a block copolymer wasobtained.

29.3 Grams of palladium on carbon (palladium-carrying amount: 5 mass. %)as a hydrogenation catalyst were added to the reaction mixed liquid, andthen a hydrogenation reaction was performed at a hydrogen pressure of 2MPa and 150° C. for 10 hours. After the resultant had been left standingto cool and the pressure had been discharged, the palladium on carbonwas removed by filtration, and then the filtrate was concentrated andvacuum-dried to provide a hydrogenated block copolymer (A′-2).

Table 1 shows the results of the measurement of the physical propertiesof the resultant hydrogenated block copolymer (A′-2).

Comparative Example 3

3,000 Milliliters of cyclohexane as a solvent and 9.2 ml ofsec-butyllithium (cyclohexane solution) having a concentration of 10.5mass % as an initiator were loaded into a pressure-resistant containerthat had been replaced with nitrogen and dried, and then the temperatureof the mixture was increased to 54° C. After that, 100 ml of styrenewere added to the mixture and then the whole was polymerized for 60minutes.

After that, at the temperature, 4.1 ml of isoprene and 5.9 ml ofbutadiene were added to the resultant at substantially the same time inone stroke, and then the mixture was subjected to a reaction. After theresultant had been left to stand for 1.4 minutes, the same amounts ofisoprene and butadiene as those described in the foregoing were added tothe resultant at substantially the same time in one stroke, and then themixture was subjected to a reaction. The foregoing operations wererepeatedly performed to finally add a total of 256 ml of isoprene and atotal of 369 ml of butadiene. After that, a reaction was forced for anadditional 90 minutes.

Further, at the temperature, 100 ml of styrene were added to theresultant and then the mixture was polymerized for 60 minutes. Afterthat, the polymerization was stopped with 0.52 ml of methanol. Thus, apolymerization reaction liquid containing a block copolymer wasobtained.

29.3 Grams of palladium on carbon (palladium-carrying amount: 5 mass %)as a hydrogenation catalyst were added to the reaction mixed liquid, andthen a hydrogenation reaction was performed at a hydrogen pressure of 2MPa and 150° C. for 10 hours. After the resultant had been left standingto cool and the pressure had been discharged, the palladium on carbonwas removed by filtration, and then the filtrate was concentrated andvacuum-dried to provide a hydrogenated block copolymer (A′-3).

Table 1 shows the results of the measurement of the physical propertiesof the resultant hydrogenated block copolymer (A′-3).

TABLE 1 Example Comparative Example 1 2 3 4 5 1 2 3 Hydrogenated block(A-1) (A-2) (A-3) (A-4) (A-5) (A′-1) (A′-2) (A′-3) copolymer Styrenecontent (mass %) 30 30 32 30 30 30 30 30 Isoprene/1,3-butadiene 45/5543/57 47/53 45/55 52/48 56/44 40/60 43/57 (mass ratio) Weight-average97,400 96,500 107,700 97,100 96,900 97,900 99,700 98,400 molecularweight Molecular weight 1.03 1.02 1.03 1.03 1.02 1.03 1.03 1.03distribution Hydrogenation ratio (%) 98.2 97.6 98.0 98.1 98.2 98.2 97.698.4 Amount of 1,4-bonds (%) 93 92 92 93 92 93 93 93 Crystallizationpeak 6.7 11.8 10.3 13.2 1.0 -5.1 16.1 19.6 temperature (° C.) Crystalmelting heat 19.1 23.7 20.3 20.7 17.2 13.7 22.4 24.8 quantity (mJ/mg)Glass transition −52 −52 −53 −50 −53 −54 −50 −52 temperature (° C.)Tensile strength (MPa) 43.2 42.8 42.4 41.4 38.2 34.5 47.3 42.3 Elasticrecovery 0.49 0.34 0.38 0.34 0.55 0.63 0.28 0.18 Abrasion resistance 143145 144 147 147 152 141 148 (mm³)

Examples 6 to 13 and Comparative Examples 4 to 6

Each of the hydrogenated block copolymers produced in Examples 1 to 5and Comparative Examples 1 to 3, the polystyrene-based resin (B′), andthe softener for a rubber (C) were blended at ratios (unit: part(s) bymass) shown in Table 2. Further, 0.1 mass % of a phenol-basedantioxidant “IRGANOX 1010” with respect to all components was added andthen the components were preliminarily mixed. After that, the mixturewas melted and kneaded with a Brabender mixer at 230° C. for 5 minutesto provide a thermoplastic elastomer composition. Table 2 shows theresults of the measurement of the physical properties of the resultantthermoplastic elastomer composition.

TABLE 2 Comparative Example Example 6 7 8 9 10 11 12 13 4 5 6Hydrogenated block copolymer (A) (A-1) 55 60 62 70 (A-2) 55 (A-3) 55(A-4) 55 (A-5) 55 (A′-1) 55 (A′-2) 55 (A′-3) 55 Polystyrene based 15 1515 15 15 6 8 10 15 15 15 resin (B′) ^(*1) Softener 30 30 30 30 30 34 3020 30 30 30 for a rubber (C) ^(*2) Tensile strength 24.7 25.4 24.0 24.821.6 22.9 25.5 31.3 20.3 26.2 25.3 (MPa) Elastic recovery 0.83 0.75 0.780.71 0.84 0.83 0.81 0.72 0.88 0.66 0.60

Description of notes in Table 2

*1: A GPPS (trade name: 679, manufactured by PS Japan Corporation,MFR=18 g/10 mm, weight-average molecular weight: 199,000)*2: A paraffin-based process oil (trade name: Diana Process Oil PW-90,manufactured by Idemitsu Kosan Co., Ltd., kinetic viscosity at 40° C.:95.54 mm²/s)

It is understood from the results of Table 1 that the hydrogenated blockcopolymer (A) of the present invention is excellent in both tensilestrength and elastic recovery, and has good abrasion resistance. It isunderstood from the results of Table 2 that a thermoplastic elastomercomposition containing the hydrogenated block copolymer is excellent inboth tensile strength and elastic recovery. In addition, it can be saidthat the abrasion resistance of the thermoplastic elastomer compositioncontaining the hydrogenated block copolymer (A) of the present inventionis also good because the abrasion resistance of the hydrogenated blockcopolymer (A) is good.

INDUSTRIAL APPLICABILITY

The hydrogenated block copolymer of the present invention is excellentin tensile strength, elastic recovery, abrasion resistance, flexibility,and weatherability, and is free of any substance that causesenvironmental pollution. Accordingly, the copolymer can be used invarious fields such as daily necessities, industrial goods, automobilesupplies, home appliances, food containers, packaging materials, medicalsupplies, miscellaneous goods, and sporting goods by taking advantage ofits features.

1. A hydrogenated block copolymer, which is obtained by hydrogenating ablock copolymer comprising: two or more polymer blocks (a) eachcomprising a structural unit derived from an aromatic vinyl compound,and one or more polymer blocks (b) each comprising structural unitsderived from isoprene and 1,3-butadiene, wherein the hydrogenated blockcopolymer has a crystallization peak temperature of −3 to 15° C.,wherein the crystallization peak temperature is defined as a peak toptemperature of an exothermic peak observed when a temperature of asample is increased from 30° C. to 150° C. at a rate of temperatureincrease of 10° C./min and then the sample is cooled to −100° C. at arate of temperature decrease of 10° C./min, the peak top temperaturebeing measured with a differential scanning calorimeter.
 2. Thehydrogenated block copolymer of claim 1, wherein a mass ratio of thestructural unit derived from isoprene to the structural unit derivedfrom 1,3-butadiene is in a range from 49.9/50.1 to 40.1/59.9.
 3. Thehydrogenated block copolymer of claim 1, wherein a content of thepolymer blocks (a) in the hydrogenated block copolymer is 20 to 34 mass%.
 4. A thermoplastic elastomer composition, comprising: thehydrogenated block copolymer (A) of claim 1; and a thermoplastic resin(B).
 5. A thermoplastic elastomer composition, comprising: thehydrogenated block copolymer (A) of claim 1; a thermoplastic resin (B);and a softener for a rubber (C).
 6. The thermoplastic elastomercomposition of claim 5, wherein in 100 parts by mass of a total of thehydrogenated block copolymer (A), the thermoplastic resin (B), and thesoftener for a rubber (C), a content of the hydrogenated block copolymer(A) is 50 to 80 parts by mass, a content of the thermoplastic resin (B)is 5 to 30 parts by mass, and a content of the softener for a rubber (C)is 10 to 45 parts by mass.
 7. The thermoplastic elastomer composition ofclaim 5, wherein the thermoplastic resin (B) comprises apolystyrene-based resin (B′).
 8. The hydrogenated block copolymer ofclaim 2, wherein a content of the polymer blocks (a) in the hydrogenatedblock copolymer is 20 to 34 mass %.
 9. A thermoplastic elastomercomposition, comprising: the hydrogenated block copolymer (A) of claim2; and a thermoplastic resin (B).
 10. A thermoplastic elastomercomposition, comprising: the hydrogenated block copolymer (A) of claim3; and a thermoplastic resin (B).
 11. A thermoplastic elastomercomposition, comprising: the hydrogenated block copolymer (A) of claim8; and a thermoplastic resin (B).
 12. A thermoplastic elastomercomposition, comprising: the hydrogenated block copolymer (A) of claim2; a thermoplastic resin (B); and a softener for a rubber (C).
 13. Athermoplastic elastomer composition, comprising: the hydrogenated blockcopolymer (A) of claim 3; a thermoplastic resin (B); and a softener fora rubber (C).
 14. A thermoplastic elastomer composition, comprising: thehydrogenated block copolymer (A) of claim 8; a thermoplastic resin (B);and a softener for a rubber (C).
 15. The thermoplastic elastomercomposition of claim 12, wherein in 100 parts by mass of a total of thehydrogenated block copolymer (A), the thermoplastic resin (B), and thesoftener for a rubber (C), a content of the hydrogenated block copolymer(A) is 50 to 80 parts by mass, a content of the thermoplastic resin (B)is 5 to 30 parts by mass, and a content of the softener for a rubber (C)is 10 to 45 parts by mass.
 16. The thermoplastic elastomer compositionof claim 13, wherein in 100 parts by mass of a total of the hydrogenatedblock copolymer (A), the thermoplastic resin (B), and the softener for arubber (C), a content of the hydrogenated block copolymer (A) is 50 to80 parts by mass, a content of the thermoplastic resin (B) is 5 to 30parts by mass, and a content of the softener for a rubber (C) is 10 to45 parts by mass.
 17. The thermoplastic elastomer composition of claim14, wherein in 100 parts by mass of a total of the hydrogenated blockcopolymer (A), the thermoplastic resin (B), and the softener for arubber (C), a content of the hydrogenated block copolymer (A) is 50 to80 parts by mass, a content of the thermoplastic resin (B) is 5 to 30parts by mass, and a content of the softener for a rubber (C) is 10 to45 parts by mass.
 18. The thermoplastic elastomer composition of claim6, wherein the thermoplastic resin (B) comprises a polystyrene-basedresin (B′).